The methods which draw a design on a formed article at low cost include insert- and in-mold molding techniques. In the insert molding, a film or sheet such as a polyester, a polycarbonate and an acrylic resin which has been decorated by, for example, printing, is preformed into a given three-dimensional shape by, for example, vacuum molding to remove an unnecessary part of the film or the sheet and then transferred into a mold for injection molding before it is combined with a resin to be a base by injection molding to give an integrated molded item. On the other hand, in in-mold molding, a film or sheet such as a polyester, a polycarbonate and an acrylic resins which has been decorated by, for example, printing, is placed in a mold for injection molding and then vacuum molded before in the same mold, it is combined with a base resin to be a base by injection molding to give an integrated molded item.
As an acrylic resin film material having good surface hardness and heat resistance which can be used in insert- or in-mold molding, there have been disclosed an acrylic resin film material prepared by mixing a rubber-containing polymer having a particular composition with a thermoplastic polymer having a particular composition in a particular ratio (See, for example, Japanese Patent Application Laid-open Nos. 8-323934, 11-147237, 2002-800678 and 2002-80679). Such acrylic resin film materials can provide a molded item with decorativeness as well as act as an alternate material for clear painting.
Furthermore, there have been disclosed an acrylic resin film material containing a rubber-containing polymer having a particular composition and a thermoplastic polymer having a particular composition in a particular ratio or containing a rubber-containing polymer having a particular composition, a thermoplastic polymer having a particular composition and a matting agent in a particular ratio (See, for example, Japanese Patent Application Laid-open Nos. 10-237261 and 2002-361712). Such an acrylic resin film material can provide a molded item with decorativeness as well as act as an alternate material for mat painting.
There have been suggested an acrylic resin laminate film prepared by laminating an acrylic resin layer substantially free from rubber particles at least one side of an acrylic resin layer containing rubber particles for providing an acrylic resin film exhibiting good surface hardness and excoriation resistance which can be used in in-mold- or insert molding (See, for example, Japanese Patent Application Laid-open Nos. 4-166334 and 2002-292808).
Similarly, addition of rubber particles may cause deterioration in weather resistance and/or chemical resistance. Therefore, there have been also suggested a laminate film prepared by laminating a fluororesin such as a vinylidene fluoride exhibiting good weather resistance and chemical resistance and good adhesiveness to an acrylic resin, on at least one side of an acrylic resin layer containing rubber particles (See, for example, Japanese Patent Application Laid-open No. 3-288640).
Furthermore, there have been disclosed a photocurable film or sheet applicable to in-mold or insert molding, comprising, on their surface, a photocurable resin exhibiting good abrasion resistance, weather resistance and chemical resistance without stickiness as well as good processability and storage stability, which can be advantageously used for manufacturing a molded item with a good design (See Japanese Patent Application Laid-open Nos. 2002-80550 and 2002-79621). Such a photocurable film or sheet may provide a molded item with decorativeness and also act as an alternate material for painting.
There have been also disclosed a laminate film or sheet prepared by laminating an acrylic resin film or sheet as an acrylic resin layer, which can be suitably used in insert- or in-mold molding (See, for example, Japanese Patent Application Laid-open Nos. 2000-86853, 2001-232660, 2001-334609 and 2002-3620).
There have been also disclosed an acrylic resin film material consisting of a multilayer structure polymer containing a rubber component exhibiting good processability and flexibility, which can be used in in-mold molding (See, for example, Japanese Patent Application Laid-open No. 8-267500).
Since an acrylic resin film material consisting of a rubber-containing acrylic resin have good properties such as transparency, weather resistance, flexibility and processability, they have been used as a surface material, a marking film and a film for coating a high-intensity reflector in, for example, vehicle internals and externals and construction material applications such as furniture, door materials, window frames, base boards and bath internals, by laminating it on the surface of a variety of resin molded items, wood products and metal molded items.
Various resin compositions have been suggested and practically used as a starting material for acrylic resin film material used in the above applications. Among others, multilayer structure polymers having a particular structure comprising, as the polymer components, an alkyl acrylate, an alkyl methacrylate and a graft crosslinker are particularly known as a starting material for an acrylic resin film material exhibiting good weather resistance, transparency and stress-whitening resistance such as bending-whitening resistance (See, for example, Japanese Patent Publication Nos. 62-19309 and 63-8983). Furthermore, there have been disclosed multilayer structure polymers as an acrylic resin film material exhibiting comparable properties (See, for example, Japanese Patent Application Laid-open Nos. 11-60876, 11-335511 and 2001-81266). There have been additionally disclosed thermoplastic resin compositions consisting of a multilayer structure polymer having a particular structure and a hydroxy-containing straight-chain polymer as a thermoplastic resin composition providing an acrylic resin film material exhibiting good matting performance (See, for example, Japanese Patent Application Laid-open No. 7-238203).
Recently, a member having an acrylic resin film material layer in its surface layer, which is formed by insert- or in-mold molding has been used as a component for vehicle applications.
An acrylic resin film material exhibiting good surface hardness, heat resistance and moldability can be obtained by adding a rubber-containing polymer having a particular average particle size (See, for example, Japanese Patent Application Laid-open No. 8-323934). An acrylic resin film material as a paint alternate exhibiting good transparency can be obtained by using a rubber-containing polymer having an average particle size of less than 0.2 μm (See, for example, Japanese Patent Application Laid-open No. 2002-80678). An acrylic resin film material as a paint alternate exhibiting both plasticizer-whitening resistance and moldability can be obtained without deterioration in surface hardness and heat resistance, by using a rubber-containing polymer having a particular structure (See, for example, Japanese Patent Application Laid-open No. 2002-80679). There has been suggested an acrylic resin film material from a rubber-containing polymer having a hard core structure with a Tg of about 105° C., which can provide an acrylic resin film material exhibiting good surface hardness (See, for example, Japanese Patent Application Laid-open No. 11-147237). An acrylic resin film material exhibiting good matting performance, surface hardness, heat resistance and moldability can be obtained by using a matting agent and a particular amount of a rubber-containing polymer having a particular average particle size (See, for example, Japanese Patent Application Laid-open No. 10-237261). There has been prepared an acrylic resin film material exhibiting good printability, matting performance, surface hardness, heat resistance and moldability and having a particular film surface glossiness (See, for example, Japanese Patent Application Laid-open No. 2002-361712). These acrylic resin film materials, however, exhibit insufficient molding-whiting resistance.
Specifically, (1) when punching for removing, in insert molding, a laminate sheet prepared by laminating an acrylic resin film material or acrylic resin film material after vacuum molding, or for removing, in in-mold molding, an acrylic resin film material protruding from a base resin, whitening is caused at the end of a molded item, leading to deterioration in a design in the molded item; (2) whitening occurs during removing a molded item having an undercut design from a mold; (3) when using a mold having convexes or concaves for forming a molded item having an irregular design such as a character, an acrylic resin film material in the concaves or convexes fails to follow the mold even after vacuum or pressure molding and a base resin must be injection-molded at an acrylic resin film material temperature of less than Tg, so that film extension by a resin pressure may cause whitening and sometimes breakage.
Because of the above problem related to molding whitening resistance of an acrylic resin film material, the material requires removing a protruding film manually instead of punching, has restrictions in its design and sometimes requires the step of removing whiteness by re-heating a whitened part, and therefore, has not been industrially useful.
For example, there have been obtained acrylic resin film materials exhibiting good weather resistance, solvent resistance, stress-whitening resistance, water-whitening resistance and transparency or matting performance (See, for example, Japanese Patent Publication Nos. 62-19309 and 63-8983, and Japanese Patent Application Laid-open Nos. 11-60876, 11-335511, 2001-81266 and 7-238202). These documents have not described insert molding or in-mold molding of an acrylic resin film material obtained, or surface hardness or heat resistance thereof. The acrylic resin film materials having the compositions described in Examples therein have insufficient level of surface hardness or heat resistance required for vehicle applications. There has been described an acrylic resin film material exhibiting good processability and flexibility and in-mold molding thereof (See, for example, Japanese Patent Application Laid-open No. 8-267500), but as is in the above acrylic resin film material, its surface hardness or heat resistance is inadequate to vehicle applications.
An acrylic resin laminate film exhibiting good excoriation resistance can be prepared by laminating a resin layer comprising an alkyl methacrylate having an alkyl group having 1 to 4 carbon atoms as a main component and having a Rockwell hardness of 90 or higher in M scale on at least one side of an acrylic resin layer containing rubber particles (See, for example, Japanese Patent Application Laid-open No. 4-166334).
However, the acrylic resin layer containing rubber particles as described in the document has lower surface hardness, so that there is room for improving surface hardness (excoriation resistance) of the final acrylic resin laminate film for using in vehicle applications. For the acrylic resin laminate film described in Examples therein, the process conditions for preparing a satisfactory molded item have narrower allowance and thus depending on the process conditions, there may occur cracks, rupture, peeling in a laminating part and the like in the acrylic resin layer. Specifically, there are restrictions to a process temperature of an acrylic resin laminate film, an injection speed of a base resin and the like, leading to lower industrial usefulness.
Furthermore, an acrylic resin laminate film which exhibits proper surface hardness and flexibility when applying to a molding process comprising bending or pulling and can provide a molded item with less molding whitening can be obtained by laminating a hard layer consisting of an acrylic resin having a bend elastic constant of 1600 MPa or more on at least one side of a soft layer consisting of an acrylic resin containing rubber particles and having a bend elastic constant of 1500 MPa or less (See, for example, Japanese Patent Application Laid-open No. 2002-292808).
The document has described molding whitening resistance, which is evaluated by conducting a tensile test in accordance with JIS K7113-1995 “Tensile test procedure for plastics” and determining a haze of a ruptured part before and after the rupture. In evaluation of molding whitening resistance in the tensile test, a haze after the test considerably varies, depending on the test conditions such as a tensile rate, a temperature condition, an inter-chuck distance and an inter-chuck distance at an end point. However, there are no descriptions of the test conditions in the document and thus, evaluation of molding whitening resistance therein is ambiguous.
In addition, there are no specific descriptions of a composition of the two-layer structure acrylic rubber used in an acrylic resin laminate film described in Examples therein.
Thus, we have prepared an acrylic resin laminate film described in Examples therein using a well-known two-layer structure acrylic rubber (See, for example, Japanese Patent Application Laid-open No. 2002-80678) having an average particle size of about 75 nm when being mixed in an acrylic resin and then conducted insert- or in-mold molding, and have observed molding whitening but not cracks, rupture or peeling in a laminating part in the acrylic resin laminate film in Example 1 therein in which an acrylic resin containing rubber particles is used as a hard layer.
In the acrylic resin laminate films in Examples 2 to 4 therein prepared by using an acrylic resin containing no rubber particles as a hard layer, cracks, rupture and peeling have generated in a laminating part in an acrylic resin layer, depending on the process conditions. Specifically, there are restrictions to a process temperature of an acrylic resin laminate film, an injection speed of a base resin and the like, leading to lower industrial usefulness.
The document has stated that molding whitening resistance can be improved by using a hard layer consisting of an acrylic resin having a bend elastic constant of 1600 MPa or more which is substantially free from rubber particles. However, molding whitening during the above insert- or in-mold molding occurs in a soft layer as a major part of the acrylic resin laminate film and therefore, whitening can be observed even in a woodgrain printing pattern in which molding whitening is relatively obscured, leading to lower industrial usefulness.
It is because a practically satisfactory level of molding whitening resistance cannot be achieved without using rubber particles exhibiting good stress whitening resistance and having, for example, a particular taper or graft structure, as rubber particles contained in an acrylic resin film (See, for example, Japanese Patent Application Laid-open Nos. 10-237261 and 2002-361712).
However, although an improved molded item without noticeable molding whitening can be provided by using rubber particles exhibiting good stress whitening resistance and having a particular taper or graft structure which is now well-known, it is difficult to obtain a molded item exhibiting adequate surface hardness required in vehicle applications as described above.
In the acrylic resin laminate film in Example 5 in the document, its surface hardness (excoriation resistance) and heat resistance are at an inadequate level for vehicle applications.
A laminate film exhibiting good transparency, stress whitening resistance, water whitening resistance and interlayer adhesiveness can be obtained by laminating a vinylidene fluoride polymer layer exhibiting good weather resistance, solvent resistance and adhesiveness to an acrylic resin layer with an acrylic resin layer having a particular multilayer structure polymer (See, for example, Japanese Patent Application Laid-open No. 3-288640). The document has not, however, described insert- or in-mold molding of the laminate film thus obtained. Furthermore, it has not described surface hardness (excoriation resistance) or heat resistance.
There is room for improving both surface hardness (excoriation resistance) and heat resistance in the laminate films in Examples therein for using in vehicle applications.
There has been obtained a photocurable film or sheet comprising a surface photocurable resin exhibiting good abrasion resistance, weather resistance, chemical resistance, non-stickiness, processability and storage stability (Japanese Patent Application Laid-open Nos. 2002-80550 and 2002-79621).
For example, when using an acrylic resin film exhibiting good surface hardness, heat resistance and moldability as a base film or sheet for preparing a photocurable film or sheet (See, for example, Japanese Patent Application Laid-open No. 8-323934), such an acrylic resin film may have inadequate molding whitening resistance and thus the photocurable film or sheet prepared may also inadequate molding whitening resistance.
Furthermore, when using an acrylic resin film exhibiting good weather resistance, solvent resistance, stress whitening resistance, water whitening resistance, and transparency as a base film or sheet (See, for example, Japanese Patent Publication Nos. 62-19309 and 63-8983), such an acrylic resin film has inadequate heat resistance, so that in a drying step for removing a solvent after applying a photocurable resin composition to a film, the photocurable resin composition and/or the acrylic resin film are extended, leading to deterioration in excoriation resistance and surface hardness after curing. When using such an acrylic resin film, the drying conditions may be optimized to minimize an extent of extension of the acrylic resin film, but it results in a larger apparatus in the drying step and also a reduced production efficiency, leading to lower industrial usefulness. Furthermore, since a drying temperature cannot be elevated, the amount of a residual organic solvent in the photocurable resin layer cannot be reduced as described later, and thus various problems tend to be caused by the residual solvent. Surface hardness in the photocurable film or sheet after photocuring is strongly influenced by surface hardness of a film or sheet to be a base, so that surface hardness is lower in the photocurable film or sheet after photocuring when using such an acrylic resin film as a base.
There has been obtained a laminate film or sheet which can be suitably used in insert- or in-mold molding, by laminating an acrylic resin film material or sheet as an acrylic resin layer (See, for example, Japanese Patent Application Laid-open Nos. 2000-86853, 2001-232660, 2001-334609 and 2002-3620). However, there have been no descriptions of importance or a solution in terms of molding whitening resistance in a laminate film or sheet having such an acrylic resin layer.
Laminate films or sheets used for surface decoration of exterior construction members such as a sash for an opening including a window, an entrance sliding door and an entrance door (hereinafter, referred to as a “construction laminate film or sheet”) are mainly those having a structure that a surface protective layer consisting of an acrylic resin exhibiting good weather resistance is laminated on the surface of a base sheet consisting of a thermoplastic resin such as polyvinyl chloride resins. These construction laminate films or sheets have a property that the acrylic resin as a surface protective layer is resistant to degradation such as oxidation or decomposition by ultraviolet rays, as well as exhibit good compatibility with, for example, benzotriazole or benzophenone ultraviolet absorbers. Thus, it can have adequate weather resistance to protect a picture layer generally formed in a base sheet or its surface from ultraviolet rays contained in sunlight and to be satisfactorily used in exterior applications.
There have been disclosed construction laminate films or sheets where an acrylic resin film or sheet is laminated on a surface protective layer laminated by a well-known lamination method (See, for example, Japanese Patent Application Laid-open Nos. 2000-225672, 2001-1465 and 2002-347185).
Laminate films or sheets for the above applications must have the functions described below.
(1) Matte-reduction Resistance
A construction laminate film or sheet tends to encounter gloss change in its surface during manufacturing, processing or the use. Specifically, the surface of a construction laminate film or sheet is generally treated by an appropriate method such as squeezing, adding a gloss adjusting agent and forming a gloss adjusting layer to be in a desired gloss state. However, in the construction laminate film or sheet, even when a gloss state in the surface is properly adjusted during a process for manufacturing the construction laminate film or sheet, the surface tends to be glossier during a process for gluing it on the surface of a variety of bases such as an aluminum sash base and a steel door base by, for example, wrapping, or during practically using the various members thus processed after being mounted in a building such as a house, leading to design defects such as shining and uneven gloss. Such design defects are caused by softening of a thermoplastic resin layer in a surface protective layer due to elevation of a temperature of the surface of the laminate film or sheet by heating during the above processing or during the use as a construction member. Specifically, matte-reduction resistance required for the laminate film or sheet corresponds to heat resistance of the thermoplastic resin layer in the surface protective layer.
(2) Secondary Processing Suitability
A construction laminate film or sheet is generally used after gluing on a variety of bases including wood bases such as a plywood and a particle board; woody bases such as a medium density fiber board (MDF); inorganic bases such as a calcium silicate board, a slate board and a cement excelsior plate; and synthetic resin bases such as a fiber-reinforced plastic (FRP). It may be glued not only simply on a flat base, but also after being three-dimensionally formed on the surface of an uneven base by an appropriate method including a folding process such as V-cutting and wrapping or vacuum molding. In particular, decorative members having various types of particular three-dimensional shape have been demanded because of diversification of consumers' preference, and thus a construction laminate film or sheet has been increasingly demanded to have secondary processing suitability such as folding processability and three-dimensional moldability. For example, in a cold region, when folding a base on which a laminate film or sheet is laminated, when folding a base after forming a V-shape groove in it (V-cutting), or when conducting folding along an uneven surface of a long base (wrapping), defects such as whitening, cracks and rupture may be generated in a turned part if stress relaxation is inadequate in the surface acrylic resin layer.
(3) Excoriation Resistance
In the light of eliminating appearance defects due to excoriation during a process for producing a laminate molded item and further extending its applications to members where excoriation more frequently occurs, including a sash in an opening such as a window, an entrance sliding door and an entrance door, there has been strongly needed to provide a construction laminate film or sheet exhibiting good excoriation resistance. As a measure of excoriation resistance, an acrylic resin layer as the surface of a laminate molded item is required to have a pencil hardness of 2 B or higher. For an acrylic resin layer with a pencil hardness of 2 B or higher, a laminate molded item prepared by using the construction laminate film or sheet exhibits practically acceptable excoriation resistance, and furthermore, appearance defects due to excoriation may be reduced during the process for preparing a laminate molded item, so that it can be used in various exterior construction members such as a sash in an opening such as a window, an entrance sliding door and an entrance door.
Although Japanese Patent Application Laid-open Nos. 2000-225672, 2001-1465 and 2002-347185 have described a construction laminate film or sheet comprising an acrylic resin film in its surface protective layer, there have been no descriptions of importance of concomitantly having these properties, i. e., excoriation resistance, matte-reduction resistance and molding whitening resistance or a solution therefor. For example, Japanese Patent Application Laid-open Nos. 2000-225672 and 2001-1465 have described molding whitening resistance, but not matte-reduction resistance.
Japanese Patent Application Laid-open No. 2002-347185 has described matte-reduction resistance, but not excoriation resistance or molding whitening resistance.
Specifically, there has been described that an acrylic resin film having a glass-transition temperature of 90° C. can be used as a surface protective layer to provide a laminate film or sheet minimizing gloss variation such as matte reduction even when the surface of the laminate film or sheet is exposed to an elevated temperature of 60° C. However, the document has not specifically described a composition of the acrylic resin film or a method for determining a glass-transition temperature. Furthermore, it has not specifically described individual processes for preparing a laminate molded item or a reason for “a surface temperature of 60° C. or higher of a laminate film or sheet” which presumably takes a practical application after mounting in a building into account. Furthermore, it has not detailed processing for preparing a laminate molded item.
For using a laminate film or sheet comprising an acrylic resin film as a surface protective layer in a part demanding the highest level of heat resistance such as an external wall including a siding, a fence, a roof, a roof deck and a balcony among the applications, it is desirable that gloss variation such as matte reduction does not occur even when holding a laminate film or sheet under the atmosphere of a surface temperature of 90° C. for 24 hours.
However, the acrylic resin film (Mitsubishi Rayon Co. Ltd., HBS006 (trade name)) described in Example in the document cannot meet the requirement for heat resistance in the above applications, thus gloss change such as matte reduction occurs when holding a laminate film or sheet at a surface temperature of 90° C. for 24 hours occur, to be restrictions to use.
Furthermore, when preparing a laminate molded item having a three-dimensional shape by three-dimensionally laminating a laminate film or sheet (Mitsubishi Rayon Co. Ltd., HBS006 and HBS027 (trade name)) prepared using the acrylic resin film described in Examples in the document on a three-dimensional polyester resin base with a curvature radius of 0.5 at a temperature of 80° C., a laminate film or sheet from HBS006 showed some whitening while a laminate film or sheet from HBS027 showed whitening. Therefore, there have been restrictions to a molding temperature, processing conditions, and the like.
These examples indicate that in a construction laminate film or sheet comprising an acrylic resin film as a surface protective layer described in Japanese Patent Application Laid-open No. 2002-347185, there is room for improving molding whitening resistance and matte-reduction resistance.
There have been furthermore disclosed that a particular resin composition can be used to improve flexibility of an acrylic resin film, which exhibits so good processability that it can be used in, for example, bending with a small curvature radius and bending at a higher deformation rate (See, for example, Japanese Patent Application Laid-open No. 11-80487). There has been disclosed that a particular resin composition can be used to provide an acrylic resin film exhibiting good low-temperature processability (See, for example, Japanese Patent Application Laid-open Nos. 2002-241445 and 2003-128734). However, Japanese Patent Application Laid-open Nos. 1999-80487, 2002-241445 and 2003-128734 have not described matte-reduction resistance in the acrylic resin film. Furthermore, in an acrylic resin film prepared by using a resin composition described in Example thereof as a starting material, its expected matte-reduction resistance is inadequate to any construction application and thus it is not suitable as a construction laminate film or sheet.
When using an acrylic resin film exhibiting good heat resistance (See, for example, Japanese Patent Application Laid-open Nos. 8-323934, 11-147237, 2002-80678 and 2002-80679), an item obtained exhibits good matte-reduction resistance, but is not suitable as a construction laminate film or sheet because of its inadequate molding whitening resistance.